Identification and expression of SR45 subfamily gene in Manihot esculenta

Objective  As major members of the splicing complex, arginine/serine-rich proteins (SR) not only participate in the process of alternative splicing of plant precursor mRNA, but also play an important role in abiotic stress. SR45 gene is a member of SR gene subfamily, this study was aimed to analyze the structural characteristics and expression patterns of SR45 subfamily proteins in cassava, and provide a theoretical support for further understanding the functions of SR45 subfamily genes in cassava.

Method  The evolutionary tree of cassava SR gene family was reconstructed by bioinformatics, and the physical and chemical properties, gene structure and conserved domain of cassava SR45 subfamily protein were analyzed. At the same time, transcriptome data were used to analyze the changes of SR gene expression under low temperature and drought stress, quantitative real-time PCR (RT-qPCR) was used to study the specific expression of SR gene members in different tissues and their responses to low temperature stress.

Result  The cassava SR gene family consisted of 26 members in seven categories, and the SR45 subfamily consisted of five members. The length of proteins encoded by SR45 subfamily genes were 135–417 aa, with relative molecular mass being 14970–47210, PI being 5.19–12.34. It was predicted that they were mainly located in the nucleus and chloroplast. The RS domain and RRM domain encoded by SR45 had Motif 3, Motif 6, Motif 2 and Motif 1 conserved motifs. Transcriptional data and RT-qPCR analysis showed that all SR45 genes were responsive to low temperature stress in cassava, MeSR45-2 was significantly up-regulated, MeSR45-4and MeSR45-5 were highly expressed in roots and leaves of cassava.

Conclusion  SR45 subfamily genes of cassava significantly respond to low temperature stress. MESR45-2 gene is selected as the candidate gene for regulating low temperature stress, root and leaf are the main tissues for SR45 subfamily gene research. This study lays a theoretical foundation for the exploration of cassava SR45 gene, and points out a direction for further research on cassava SR45 gene responsive to stress.